1. Industrial Field of the Invention
The present invention relates to a disk drive apparatus, e.g. a floppy disk system, a hard disk system or the like, used as an external memory or the like for a computer, and it also relates to a bearing device for use in such the disk drive apparatus.
2. RELATED ART
Referring to FIG. 8, in the structure of a conventional disk drive apparatus, a substrate 4, a stator 3, a metal bush 13 and a bearing unit 12 are attached on an aluminum die-cast base 11. Further, a magnet 5, a rotor yoke 6, a hub magnet 7, a hub 8 and a shaft 9 are assembled, and the shaft 9 is provided in the metal bush 13 and the bearing unit 12. Thus, the direct drive motor is constituted.
In the conventional disk drive apparatus, however, the metal based printed circuit board 4 which can be subjected to magnetization required for the motor is provided on the aluminum die-cast base 11 serving as a casing, and also, the bearing unit 12 is closely fitted in a bearing housing which is integrally formed with or securely connected on the aluminum die-cast base 11 so as to fix the shaft 9. Consequently, it is difficult to decrease such an apparatus in thickness and size. Moreover, the conventional apparatus involves a problem of difficulty in simplification of the machining procedure, and an economic problem of expenses for a die for aluminum die casting, finish machining and so forth.
A bearing device 10 itself can not be reduced in thickness since it comprises the metal bush 13, the bearing unit 12 and so forth so that a height h from the bottom surface of the base 11 of the bearing device 10 to the hub 8 is 10 mm or more. Further, as shown in FIG. 9, deflection of the shaft 9 is as large as 10 .mu.m at minimum to 20 .mu.m at maximum, and therefore, the bearing device 10 involves a problem that high accuracy in supporting the shaft 9 can not be obtained.
Besides, the number of component parts such as the metal bush 13 and the bearing unit 12 is so large that the cost is high, and the bearing unit 12 involves a problem that it is low in vibration and impact strength.